Hi ... i have taken my imac 27" in to the mac shop because it was experiencing a black screen - originally intermittent flashing to the last two weeks of blacking out every 15 minutes ... the monitor attached to the computer was working fine whenever the computer went black. so all is well with the HD. it was confirmed in the shop that all is well with HD. they thought it was the fan ... and now they are saying its the graphics card which cannot be replaced? upon questioning i am told that things dont last longer than 5 years and they cannot replace it ????/ i just cant get my head around this ... it cannot possibly be so? the machine is a 2010 model and is very very well looked after -r egular shop visits to reset and updates, etc. can someone please advise ???